Hi Caribsurf,
I checked the website and it looks like your board came with a 48 cm fin.
The 48 cm should be about right for your 7.5 m2 Focus.
If you want a little earlier planing, perhaps a 50-52 cm would get you planing slightly earlier. The 48 cm could also work with your 6.0 Focus but at the top this sail's range
something about 38-42 cm could give you a little more speed and control.
The 5.5 m2 is on the small size for the 133, but if you are overpowered on your 6.0,
the 5.5 will work fine on the GO 133.
As far as I know the shapes of the Futura 133 and Go TufSkin 133 are identical, but the
TufSkin boards weigh 2-3 Kg. more.
Hope this helps!

i use 48 en 52 fins under my GO (both Drake R13). The 48 works best with sails between 6,5 and 7,5 but a 6,0 is perfectly doable. below 6.0 you should get better results with a 44 fin. I use the 52 fin for earlier planning on low winds with 7,5 like roger suggest and with a 8,8 sail. In both cases it works perfectly!

Hi CS,
Yes, the MFC "Liquid Pro" in a 44 or 48 cm with a Tuttle base should work pretty good in your GO 133.
You may have to do some "fitting" to get the new fin into your fin box correctly, but all fins normally require a little bit of filing and fitting to really fit your fin box solidly.
$140 may sound a little pricey, but unless you buy a used fin, that's probably about the going rate.
You can get some Marine Tex and repair your existing fin.
Just file and sand the large gouges to fair them to the surrounding area, then fill the holes, gaps and gouges with marine tex.
Use wide masking tape to fair the Marine Tex to the undamged area around the damage, starting the tape on one side, filling in the tape with the repair material, then folding the tape over and sticking the other side down.
The use your fingers to "fair" in the tape as close as you can.
You can "cure" the Marine Tex fairly quickly in a 120-150 deg. oven.
Remove the tape, and use a file to smooth the repair and fair it to the surrounding area.
Finish up with a sponge sanding block and you can repair your fin back to it's original shape.
The Marine Tex won't handle impacts quite as well as your original fin did, but if it gets chipped out, you can easily fill it back in again.
Used stock fins are normally pretty easy to find on the internet, and you can ge some really good high performance fins for not too much money as well, online.
It's really a good idea to have about 3 or 4 fins for a board like the GO 133.
The stock fin, and two extra fins (one about 4 cm larger than the stock and one about
4-6 cm smaller).
Also you might want to have a weed fin or 2. Get something like the Lessacher Duo Weed and you may end up sailing the weed fin all the time as they don't get damaged as easily as vertical fins.
Also the shorter swept back weed fins allow you to sail far more safely in much shallower water as they "ride up" if you strike a rock or sandbar.
Hope this helps,